I try to calculate groupby pct_changeusing df.groupby('type')['value'].apply(lambda x: x.pct_change()) for a dataframe.
But it generates ValueError: cannot reindex from a duplicate axis, any ideas how to deal with this issues? Thanks.
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You very likely have duplicate values in your index . Check this link stackoverflow.com/questions/27236275/…moys– moys2019-12-13 05:21:48 +00:00Commented Dec 13, 2019 at 5:21
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I get this same error if i have duplicates in my index. You'll need to reset_index():
In [726]: df.append(df)
Out[726]:
customer brand product quantity price new_quantity
0 C1 B1 P1 100 5 500
1 C1 B1 P2 10 20 200
2 C1 B2 P3 50 7 350
3 C2 B1 P1 75 5 375
4 C2 B2 P3 5 7 35
0 C1 B1 P1 100 5 500
1 C1 B1 P2 10 20 200
2 C1 B2 P3 50 7 350
3 C2 B1 P1 75 5 375
4 C2 B2 P3 5 7 35
df.groupby('customer')['quantity'].apply(lambda x: x.pct_change())
# ValueError: cannot reindex from a duplicate axis
In [730]: df.append(df).reset_index().groupby('customer')['quantity'].apply(lambda x: x.pct_change())
Out[730]:
0 NaN
1 -0.900000
2 4.000000
3 NaN
4 -0.933333
5 1.000000
6 -0.900000
7 4.000000
8 14.000000
9 -0.933333
Name: quantity, dtype: float64
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ah bon
I try with my real data, the code works, but results seems not correct. ;(